Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
To provide cellular wireless communication service, a wireless service provider typically operates a radio access network (RAN) that includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
In general, a RAN may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to UEs defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies or blocks of frequencies (e.g., frequency bands, such as 698-960 MHz, 1610-2025 MHz, etc.) and may define a number of air interface channels for carrying information between the base station and UEs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing, for instance. By way of example, each coverage area may define a pilot channel, reference channel, or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage strength. As another example, each coverage area may define one or more uplink control channels or other resources on which UEs may transmit control messages to the base station. And each coverage area may define one or more downlink control channels or other resources on which the base station may transmit control messages or other information to UEs. Further, each coverage area may define one or more traffic channels or other resources for carrying bearer communication traffic such (e.g., user traffic or application level traffic) as voice data and other data between the base station and UEs.
When a UE first powers on or enters into coverage of the RAN, the UE may scan the pilot or reference signals of the RAN's coverage areas in an effort to identify a strongest coverage area. The UE may then register with the RAN in that coverage area by transmitting a registration request, attach request, or the like to the base station serving that coverage area, and perhaps engaging in further registration signaling with the base station.
Once the UE is registered in the coverage area, the UE may then operate in an idle mode or a connected mode. In the idle mode, the UE may not have any assigned traffic channel resources on which to engage in bearer communication with the base station. However, if the UE seeks to establish bearer communication (at the UE's initiation, or in response to a page message from the base station for instance), the UE may transmit an access or connection request on an uplink access channel to the base station, to request assignment of traffic channel resources. And upon receipt of that request, the base station may then assign a traffic channel or other radio link resources to the UE, thereby transitioning the UE to the connected mode, so that the UE and base station can exchange bearer communications with each other.
When a UE communicates with a base station, the UE and base station may engage in a power control process to help manage the transmission power that the UE uses for transmission to the base station. In particular, as the UE transmits to the base station, the base station may evaluate the strength at which the base station receives the UE's transmissions and may transmit power control commands to the UE to cause the UE to adjust its transmission power. In an example implementation of such a process, if the base station determines that the receive signal strength from the UE is lower than a threshold level, the base station may transmit a power-up command to the UE, and the UE may responsively increment its transmission power. Whereas, if the base station determines that the receive signal strength is higher than the threshold level, the base station may transmit a power-down command to the UE, and the UE may responsively decrement its transmission power. Through this process, the base station and UE may thus work to reach a suitable UE transmission power, such as one at which the base station's receive signal strength is at or about the threshold level.